Air Quality Studies, Department of Civil and Environmental Engineering, The Hong Kong Polytechnic University, Hong Kong, China.
Environ Sci Process Impacts. 2019 Jun 19;21(6):916-929. doi: 10.1039/c9em00098d.
Ozone (O3), a main component in photochemical smog, is a secondary pollutant formed through complex photochemical reactions involving nitrogen oxides (NOx) and volatile organic compounds (VOCs). In the past few decades, with the rapid economic development, industrialization and urbanization, the mixing ratio of O3 has increased substantially in China. O3 non-attainment days have been frequently observed. Despite great efforts made in the past few years, it is still difficult to alleviate O3 pollution in China, due to its non-linear relationship with the precursors. In view of the severe situation in China, this study presents a comprehensive review on the spatial-temporal variations of the relationship between O3 and its precursors (i.e. O3 formation regime), built upon the previous reviews of the spatial-temporal variations of O3 and its precursor levels. Valuable findings from previous studies are laid out for a better understanding of O3 pollution, followed by implications for the control of O3 pollution. This literature review indicates that O3 formation in most areas of the North China Plain (NCP), Yangtze River Delta (YRD) and Pearl River Delta (PRD) regions is in a VOC-limited regime during the high-O3 seasons due to dramatic emissions from human activities in cities. Outside these metropolitan areas, a NOx-limited regime dominates rural/remote areas. From summer to winter, the O3 formation regime over China shows a tendency to shift to a VOC-limited regime. Furthermore, O3 formation in China shifted toward increasing sensitivity to VOC emissions before the 12th Five-Year-Plan. However, after the 12th Five-Year-Plan, successful reduction of NOx slowed down this trend. Further effective control of VOCs is expected to achieve sustained O3 attainment in the future. To timely solve the current O3 pollution problem, precise control of O3 precursors is proposed, together with the joint prevention and control of regional air pollution.
臭氧（O3）是光化学烟雾的主要成分之一，是通过涉及氮氧化物（NOx）和挥发性有机化合物（VOCs）的复杂光化学反应形成的二次污染物。在过去几十年中，随着经济的快速发展、工业化和城市化，中国的 O3 混合比大幅增加。O3 未达标天数频繁出现。尽管过去几年做出了巨大努力，但由于其与前体物的非线性关系，中国仍难以缓解 O3 污染。鉴于中国的严峻形势，本研究在对 O3 和前体物（即 O3 形成机制）时空变化的先前综述基础上，对 O3 和前体物之间关系的时空变化进行了全面综述。为了更好地理解 O3 污染，列出了先前研究的有价值的发现，并提出了控制 O3 污染的启示。本文献综述表明，在中国华北平原（NCP）、长江三角洲（YRD）和珠江三角洲（PRD）地区的大部分地区，由于城市人类活动的剧烈排放，高 O3 季节的 O3 形成处于 VOC 限制机制。在这些大都市区之外，NOx 限制机制占主导地位的是农村/偏远地区。从夏季到冬季，中国的 O3 形成机制呈现出向 VOC 限制机制转变的趋势。此外，在中国，O3 形成对 VOC 排放的敏感性在“十二五”规划之前呈增加趋势。然而，“十二五”规划之后，NOx 的成功减排减缓了这一趋势。预计进一步有效控制 VOCs 将实现未来 O3 的持续达标。为了及时解决当前的 O3 污染问题，提出了对 O3 前体物的精确控制，以及区域空气污染的联合防治。
